Gun



Oct. 31, 1933- c. E. SIMPSON ET AL 1,932,424

GUN

Filed Nov. 4, 1931 INVENTORS Clarence Efiirgpsun yNiliiTTL R ELL11 TTORNEY Patented 0a. 31, 1933 GUN Clarence E. Simpson, Springfield, and William R. Bull, Longmeadow, Mass.

' Application November 4, 1931. Serial No. 573,007

'7 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes,,without the payment to us of any royalty thereon.

This invention relates to guns and more especially to mechanism for adjusting the head space in a machine gun.

In the average gun the barrel is worn out'before other parts and needs replacement. Upon replacement of the barrel it becomes necessary to readjust the head space which is a more or less tedious task requiring removal of the action from the receiver and necessitating threading the end of the barrel with threads of a sufliciently gradual pitch to permit proper adjustment.

The main advantages of the present invention are therefore, to permit the barrel to be readily removed and replaced without disturbing or removing the action; to permit the barrel'to be locked in place by interrupted threads necessitating only a quarter turn of the barrel; to permit accurate adjustment of the head space while the gun is completely assembled. 7

These objects are attained broadly by varying the locked position of the breech bolt.

Specifically, an adjustable cam is provided to cooperate with the breech bolt lock to vary the locked position of the bolt.

- With the foregoing and other objects in View, the invention resides in the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed,

it being understood that changes in the precise embodiment of the invention herein disclosed maybe made within the scope of what is claimed without departing from the spirit of the invention.

A practical embodiment of the invention is.

illustrated in the accompanying drawing, where- Fig. 1 is a fragmentary View in longitudinal section of the action of a gun with a breech bolt lock adjusting means constructed in accordance with the invention.

Fig. 2 is an enlarged fragmentary View in longitudinal section showing the adjustment for locking the boltin its extreme forward position. Fig. 3 is a similar view showing the adjustment when the bolt is locked in its extreme rear- I ward position and,

Figs. 4 and 5 are section on the lines 44 and for slight rectilinearsliding movement the barrel I extension 7. A breech bolt 8 reciprocates in the barrel extension and is provided with a longitudinal bore 9 for the reception of. a firing pin 10,

which is cockedby a usual cocking lever 11 and 5 held in cocked position by a scar 12, adapted to be released by a trigger 13. Sliding in a guideway formed in the barrel extension is a. breech bolt lock 14 adapted to enter a recess 15 formed in the breech bolt and cooperating for that purpose with a cam block carried by the receiver. The cam block consists of a main portion 16 rigidly secured to the receiver, in this instance by means of a screw 17, which main portion is provided with a guide, herein,' shown asa recess 18 for the reception of an adjustable cam block 19 which is positioned to contact the lock 14 and force the same into the recess 15 to lock the bolt. The cam block 19 is preferably adjustable through means of a screw 20 which is threaded into the block and journaled in the receiver, and which may be locked in adjustedposition'by the lock nut 21 and washer 22. As shown. the upper forward edge of the lock 14 is angled ofi to contact the angled for- 30 ward face of the recess 15 so that by raising the" lock or adjusting it inwardly the bolt is caused to be locked in a more forward position while adjustingthe lock outwardly will cause the bolt to be locked in a more rearwardly position thus 35 increasing the head space.

As seen most clearly in Figs. 4 and 5, the barrel 23 may beprovided with interrupted threads 24 to engage complemental threads 25 formed in a forwardly projecting sleeve 26 of the barrel extension thereby providing a means for quickly attaching and detaching the barrel.

We claim:

1. The combination with a gun provided with a breech closure, of a breech closure look, a cam 9 for operating the lock, and means for adjusting the cam whereby the closure is locked with the desired spacing for the breech.

2. The combination with a gun provided with a breech closure, of a breech closure lock, a cam.. for operating the lock, and an adjusting screw for adjusting the cam whereby the closure is locked with the desired spacing from the breech.

3. The combination with a gun provided with a breech closure, of an adjustable lock for the .10 breech closure, and means on the exterior of the gun for adjusting 'the lock to vary the spacing of the locked closure from the breech.

4. The combination with a gun provided with a breech closure, of a breech closure lock, adjust- =1 able means cooperating with the lock, and means on the exterior of the gun for adjusting the adjustable means to vary the spacing of the locked closure from the breech.

5. The combination with a gun provided with a breech closure, .of a breech closure lock, a cam for operating the lock, and means on the exterior of the gun for adjusting the cam to vary the spacing of the locked closure'from the breech.

6. The combination with agun provided with a breech closure, of a lock for the breech closure, means for operating the :lock, andt means-on the 

